1. Field of the Invention
The present invention relates to a film feeding cessation adjusting device for cameras which is designed to feed individual frames of a film to a predetermined photographic position.
2. Related Background Art
Cameras capable of recording data on a magnetic recording medium coated on a data recording area of a film or reproducing data recorded on the magnetic recording medium are known.
In the film used in such a camera, the data recording area is provided on the portion of the film other than the photographing image plane so that the frames of the film are not damaged when data is recorded or reproduced using a magnetic head or the like. However, the portion of the film other than the photographing image plane has perforations used for feeding the film. In order to provide sufficient data storage capacity, the number of perforations must therefore be reduced as much as possible to provide a large data recording area.
To overcome such a problem, there has been proposed a film 1 shown in FIG. 1 and a device for controlling feeding thereof (see commonly owned U.S. Ser. No. 720,719 filed on Jun. 25, 1991).
In the film 1 shown in FIG. 1, each of the frames on the film 1 has two perforations at predetermined positions on the left and right-hand sides of and above the frame. Perforations 2a and 2b, 3a and 3b, and 4a and 4b are located at exactly the same positions in relation to their corresponding frames. Hereinafter, the perforations 2a, 3a and 4a located on the left-hand side of the frames on the film 1 are referred to as first perforations, while the perforations 2b, 3b and 4b located on the right-hand side are referred to as second perforations. Reference character P.S in FIG. 1 denotes a detection position where a photoelectric conversion device detects the perforations on the film.
In FIG. 1, the first perforation 3a of the frame 3 is located at the detection position P.S of the photoelectric conversion device. In this feed control device, when the first perforation 3a is at the detection position P.S, the frame 3 is opposite the aperture of the camera which is not shown. Hereinafter such a frame position is referred to as a reference position. In the feeding of the film 1, the frames are located accurately at the aperture by stopping the perforations located at exactly the same positions in relation to their corresponding frames at a predetermined position.
Hence, the film feed control device duty drives a feed motor and thereby decelerates a film when it detects a perforation immediately before the perforation indicating an objective stopping position during film feeding. When the perforation indicating the objective stopping position is detected, the film feed control device short brakes the feed motor to stop the film at a predetermined stopping position.
FIG. 2(a) shows the film feed motor driving output waveform when the film feeding is conducted, FIG. 2(b) shows the perforation detecting waveform of the photoelectric conversion device, and FIG. 2(c) shows the brake operating waveform.
When exposure of the frame 3 shown in FIG. 1 and located at the reference position is completed, one frame feeding is initiated at time t1 to locate a subsequent frame at the reference position. At time t2, the first perforation 3a of the frame 3 has passed the detection position P.S of the photoelectric conversion device, and the perforation detection waveform therefore falls. Thereafter, when the second perforation 3b of the frame 3 is detected by the photoelectric conversion device at time t3, duty drive of the film feed motor is initiated to decelerate the film. Thereafter, when the perforation indicating the objective stopping position, i.e., the first perforation 4a of the subsequent frame 4, is detected at time t4, duty drive of the film feed motor is stopped and braking operation is conducted to stop film feeding.
In a camera in which the film is fed at a high speed, however, deceleration of the film conducted between the two adjoining perforations is not enough, and the film may overrun beyond the objective stopping position.
Furthermore, even if braking is conducted when the perforation indicating the objective stopping position is detected, the film may not stop at once and may overrun due to the inertia of the film feeding mechanism including the motor. If the amount of overrun is fixed, each frame is stopped at substantially the same position in each frame feeding operation.
However, this amount of overrun varies, mainly in accordance with the film feeding speed when the film feeding speed reduces due to variation in battery voltage or ambient temperature, the amount of overrun required to stop the film reduces, and the film thus stops at a position immediately before the normal stopping position. Conversely, when the film feeding speed increases, the amount of overrun increases, and the film is fed beyond the normal stopping position.